linux-kernel - Re: [PATCH] cxl/acpi: fix null dereference on probe for missing ACPI

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Date:   Thu, 15 Dec 2022 09:35:22 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Davidlohr Bueso <dave@...olabs.net>,
        Luis Chamberlain <mcgrof@...nel.org>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Lucas De Marchi <lucas.de.marchi@...il.com>,
        <alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
        <ira.weiny@...el.com>, <bwidawsk@...nel.org>,
        <a.manzanares@...sung.com>, <linux-cxl@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/acpi: fix null dereference on probe for missing
 ACPI_COMPANION()

Davidlohr Bueso wrote:
> On Wed, 14 Dec 2022, Luis Chamberlain wrote:
> 
> >Groovy thanks. Progress, but still fails now on the cxl-xor-region.sh line 29
> >
> >https://gist.github.com/mcgrof/aeac639365a651bd77f143cf38eb7493
> 
> Unrelated, but looking at this log I noticed that we should limit the amount
> of noise "Bypassing cpu_cache_invalidate_memregion() for testing" emits.
> 
> Thanks,
> Davidlohr
> 
> -----8<-------------------------------------
> [PATCH] cxl/region: Only warn about cpu_cache_invalidate_memregion() once
> 
> No need for more than once per region.

Hmm, the below isn't once per region, it's once per cxl_core module
load.

> 
> Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
> ---
>   drivers/cxl/core/region.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index b1281f528d7f..f367d1c10357 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2006,8 +2006,7 @@ static int cxl_region_invalidate_memregion(struct cxl_region *cxlr)
>   
>   	if (!cpu_cache_has_invalidate_memregion()) {
>   		if (IS_ENABLED(CONFIG_CXL_REGION_INVALIDATION_TEST)) {
> -			dev_warn(
> -				&cxlr->dev,
> +			dev_WARN_ONCE(&cxlr->dev, 1,
>   				"Bypassing cpu_cache_invalidate_memregion() for testing!\n");

This will end up failing the unit tests because those want to have a
clean kernel log from a "Call Trace" perspective. So either
dev_warn_once() or just live with the noise since the message is more
for awareness in production environments and test environments can
ignore it.